JPH07173566A - Aluminum alloy casting for squeeze casting excellent in strength and toughness and production thereof - Google Patents

Abstract

PURPOSE:To produce an aluminum alloy casting for squeeze casting having mechanical properties equivalent to those of a forging material and low in cost compart to a forging material and provide a method for producing the same. CONSTITUTION:This aluminum alloy casting for squeeze casting is the one contg., by weight, 0.6 to 1.0% Si, 0.5 to 1.0% Cu, 0.5 to 1.2% Mg, 0.002 to 0.20% Ti and 0.0004 to 0.04% B, and the balance Al with inevitable impurities. The aluminum alloy molten metal having the same componental compsn. is filled into die product part at 650 to 800 deg.C molten metal temp., and after that, directional solidification is executed from the initial solidified part of the casting product to a sprue part under a high pressure of >=500kgf/cm<2>, by which the squeeze casting aluminum alloy casting is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy casting used for automobile brake parts, suspension parts, etc.
More specifically, strength compared to conventional aluminum alloy castings,
TECHNICAL FIELD The present invention relates to an aluminum alloy casting for high pressure casting having improved elongation and toughness and having performance equivalent to that of a forged product, and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum and aluminum alloys are being used for the purpose of weight reduction in automobile parts such as undercarriage parts that have conventionally used iron-based materials, and aluminum alloys are often used from the viewpoint of unsprung weight reduction. It has started to be done. As the aluminum alloy, Al-Mg-Si alloys, which have relatively good corrosion resistance and are excellent in workability, are often used, especially JIS6061 and 6N01 alloys, and forged to obtain high strength and high toughness necessary for important safety parts. Is manufactured by. However, these materials are often made by cutting an extruded material into an appropriate length, and undergo many steps such as preforming, roughing and finishing, resulting in poor yield and high manufacturing cost. It has the drawback of

On the other hand, aluminum castings are used in a considerable proportion for automobile parts because they can be manufactured in a complicated shape at low cost. As a casting alloy, Al-Cu-
(Si) type AC1B, AC2B, Al-Si type AC
3A, etc., but from the viewpoint of high strength, high toughness, and corrosion resistance, a small amount of Mg is added to an Al-Si alloy with good castability to improve the mechanical properties of Al-Si-
Cast alloys such as Mg-based AC4C and AC4CH are often used. However, since these castings have many internal defects during casting and the amount of dissolved gas is high, gas defects such as blisters and blisters are likely to occur after heat treatment. In addition, since the strength level is lower than that of a forged material and stable performance is difficult to obtain, its use is currently limited to thin materials such as cases and covers, or members having relatively low required strength.

Since cost reduction is also essential, there is a strong demand for the development of a casting material that has the same performance as a forged material and can reduce the cost. In order to satisfy this requirement, attempts have been made to overcome problems in casting by a high pressure casting method, and some parts have been put into practical use by using casting alloys (for example, Japanese Patent Laid-Open No. 61-227142). JP-A-61-227146). However, high strength and high toughness have not been obtained enough to replace the important safety parts used in the current forged products or to make them thinner. Further, it has not been possible to stably suppress variations in internal defects such as inclusion of aluminum solidified film and oxide film during filling of molten metal and occurrence of shrinkage cavities due to insufficient casting pressure.

[0005]

DISCLOSURE OF THE INVENTION The present invention increases the strength and toughness improving elements and increases the toughness inhibiting element S.
It is an object of the present invention to provide an aluminum alloy casting for high pressure casting which has mechanical performance equivalent to that of the forged material and is lower in cost than the forged material by reducing the amount of i as much as possible, and a manufacturing method thereof.

[0006]

As a result of intensive studies in view of the above situation, the present invention has an aluminum alloy casting for high pressure casting which has mechanical performance equivalent to that of the forged material and is lower in cost than the forged material, and a method for producing the same. Was developed.

That is, according to the invention of claim 1, S in weight% is used.
i 0.6 to 1.0%, Cu 0.5 to 1.0%, Mg0.
5 to 1.2%, Ti 0.002 to 0.20%, B0.0
It is an aluminum alloy casting for high pressure casting containing 004 to 0.04% and the balance being Al and unavoidable impurities.

According to the second aspect of the present invention, the S content is% by weight.
i 0.6 to 1.0%, Cu 0.5 to 1.0%, Mg0.
5 to 1.2%, Ti 0.002 to 0.20%, B0.0
004-0.04%, balance Al and unavoidable
The aluminum alloy molten metal containing impurities is melted at a temperature of 650
500kgf / cm after filling the mold product at ~ 800 ℃
²Under the above high pressure, from the initial solidification part of the casting product to the sprue part
A high pressure casting tool characterized by directional solidification
It is a method for producing a aluminum alloy casting.

[0009]

The reason for adding the additive element and the reason for limiting the added amount of the aluminum alloy casting according to the present invention will be described.
In this specification, alloy composition% means% by weight.

Si and Mg: Si and Mg are elements which coexist and are effective in precipitating Mg ₂ Si during heat treatment after casting to enhance the strength. Si is 0.6% and Mg is 0.5.
%, Sufficient strength cannot be obtained, Si is 1.0%, M
If g exceeds 1.2%, the strength is sufficient, but the toughness and corrosion resistance are significantly reduced, which is not preferable. Therefore Si
Is 0.6 to 1.0% and Mg is 0.5 to 1.2%.

Cu: Cu, together with Mg and Si, is effective in improving the strength after heat treatment, but if the addition amount is less than 0.5%, sufficient strength cannot be obtained, and if it exceeds 1.0%, the corrosion resistance deteriorates. Therefore, it is not preferable. Therefore, Cu is 0.5 to 1.
0%

Ti and B: Ti and B are effective in refining the cast structure, preventing casting cracks in the surface layer of the casting, and preventing macro segregation in the vicinity of the sprue part which is the final solidification part. Here, the addition amount is 0.002% and 0.0, respectively.
If it is less than 004%, the above effect cannot be obtained, and if it exceeds 0.20% and 0.04%, coarse inclusions are generated and mechanical performance is deteriorated, which is not preferable. Therefore, Ti 0.002 to 0.02%, B 0.0004 to
It is set to 0.04.

Next, a method for producing an aluminum alloy casting according to the present invention will be described with reference to FIG. Aluminum alloy castings reduce mechanical defects, especially internal defects that lower elongation values and obtain sound internal quality. Therefore, when the molten metal temperature at the sprue part (9) immediately before filling the product part (2) is less than 650 ° C. The solid phase ratio of the molten metal becomes high, the casting pressure after filling the product part (2) is difficult to propagate, and local shrinkage cavities are generated, which is not preferable. Also, if the temperature exceeds 800 ° C, gas is likely to be absorbed in the molten metal and gas porosity is likely to occur,
The molten metal temperature is 650 to 800 ° C. The melt temperature at the sprue part (9) immediately before filling the product part (2) is set to 650 to 80
The method of setting the temperature to 0 ° C. is to raise the temperature of the molten metal when pouring the molten metal into the plunger sleeve in the normal ladle hot water supply,
Alternatively, it is conceivable to coat the inner surface of the ladle with a heat insulating material such as ceramic to prevent the melt temperature from decreasing. However, in this method, oxide film entrainment is inevitable when pouring the molten metal from the ladle into the plunger. Therefore, as a means for transferring the molten metal from the holding furnace to the plunger sleeve (4),
It is desirable to use a method such as an electromagnetic pump or a metal pump that does not easily cause turbulence in the molten metal and has a high pouring speed.

When the molten metal filled in the product part (2) is solidified, it is directionally solidified from the initial solidification part (2a) of the casting product toward the sprue part (9) under a high pressure of 500 kgf / cm ² or more. When the casting pressure is less than 500 kgf / cm ² , shrinkage cavities and casting cracks frequently occur, and the mechanical performance, especially the elongation value, remarkably decreases, which is not preferable. In addition, the solidification is the initial solidification part (2
If the final solidification part (2b) near the sprue part (9) does not proceed sequentially from a) to the sprue part (9) and the final solidification part (2b) solidifies first, sufficient casting pressure does not propagate into the product part, so it is possible to shrink to the relevant part. Porosity and cast cracking are not preferable. As for the mold cooling method, when using a normal die casting mold, an independent water cooling pipe (6) is provided in the mold from the initial solidification part (2a) of the casting product to the final solidification part (2b) and the sprue part (9). This is easily achieved by increasing the amount of cooling water at the time of casting as much as the initial solidification part (2a) and decreasing it in the central part of the product, the final solidification part (2b) of the product, and the sprue part (9). That is, the mold cooling method is the initial solidification part (2a) of the product part.
To the final solidification part (2b). In the present specification, directional solidification refers to the solidification method described above. The initial solidification part (2a) of the casting product
Means the position of the product farthest from the sprue part (9).

The alloy casting of the present invention is heat-treated according to the required performance of the final product, but the heat-treatment conditions are not particularly limited. That is, depending on the composition of the aluminum alloy casting according to the present invention, the strength, by subjecting to solution treatment and quenching and aging treatment conditions specified in JIS,
The elongation and toughness can be adjusted.

[0016]

EXAMPLES The casting apparatus shown in FIG. 1 was used as the apparatus. This casting apparatus includes a product portion (2) formed in a mold (1), a molten metal supply path (3), a plunger sleeve (4) into which a fixed amount of molten metal is poured, and a plunger sleeve (4). It consists of a plunger tip (5) that fills and pressurizes the molten metal into the product part (2). Here, a cold water pipe (6) is passed through the mold (1) at regular intervals along the product part (2), and the amount of cold water is changed from the initial solidification part (2a) to the final solidification part (2b) to change the temperature gradient. It has a structure that can be made.

Aluminum alloys having the compositions shown in Table 1 were melted by a usual method, and degassed by Ar gas bubbling for about 20 minutes at a molten metal temperature of 750 ° C.
Using the casting apparatus of No. 2, pressure casting was performed under the casting conditions shown in Table 2 to prepare a flat plate test piece having a wall thickness of 20 mm and a width of 100 mm. The molten metal temperature was measured by a molten metal temperature measuring thermocouple (7) installed in the spout (9). The mold temperature during casting was controlled by changing the amount of water in the cold water pipe (6) at each site while casting. As for the casting pressure, the load applied to the plunger tip (5) at the time of casting was maintained as it was, and the load was divided by the cross-sectional area of the plunger tip (5) and the casting pressure is shown in Table 2.

The cross sections of these aluminum alloy castings (flat plate test pieces) were polished, and internal defects such as shrinkage cavities and casting cracks were visually observed. In addition, heat treatment (540 ℃
After solution heat treatment for 8 hours, water cooling, and aging treatment at 180 ° C. for 8 hours), then tensile test pieces and Charpy test pieces are sampled and used as index values for tensile strength, proof stress, elongation value, and toughness. The Charpy impact value was measured. The results are also shown in Table 2.

[0019]

[Table 1]

[0020]

[Table 2]

As is clear from Table 2, no internal defect was observed in the test piece in which the alloy of the present invention was cast under predetermined casting conditions.
AC4CH which has been practically used for high pressure casting
It can be seen that the strength and toughness are superior to the alloy castings.
On the other hand, when the alloy composition is not within the scope of the claims, sufficient strength and toughness cannot be obtained, and when the alloy composition is within the scope of the claims and the casting temperature or pressure is low or there is no cooling temperature gradient of the mold, It can be seen that internal defects such as shrinkage cavities and casting cracks frequently occur in the product, and mechanical performance tends to deteriorate.

[0022]

As described above, according to the present invention, as compared with a conventional aluminum alloy casting, both strength and toughness can be improved, and a casting having no internal defects such as shrinkage cavities and casting cracks can be obtained. It can be used for undercarriage parts that require high strength and high toughness and brake parts that require pressure resistance. Therefore, the same performance as conventional forgings can be obtained, so manufacturing costs can be reduced. It has a remarkable effect.

[Brief description of drawings]

FIG. 1 is a main cross-sectional view of a pressure casting device according to an embodiment.

[Explanation of sign]

 1. Mold 2. Product part 2a. Initial solidification part 2b. Final solidification part 3. Molten metal supply route 4. Plunger sleeve 5. Plunger tip 6. Cold water pipe 7. Thermocouple for measuring molten metal temperature 8. Degassing section 9. The gate

Claims (2)

[Claims] 1. Si 0.6-1.0% by weight, Cu
0.5-1.0%, Mg0.5-1.2%, Ti0.0
An aluminum alloy casting for high pressure casting, containing 02 to 0.20%, B 0.0004 to 0.04%, and the balance being Al and inevitable impurities. 2. Si 0.6-1.0% by weight, Cu
0.5-1.0%, Mg0.5-1.2%, Ti0.0
500 kgf / cm after filling an aluminum alloy melt containing 02 to 0.20% and B 0.0004 to 0.04% with the balance Al and unavoidable impurities at a melt temperature of 650 to 800 ° C. ^A method for producing a high-pressure cast aluminum alloy casting, which comprises directionally solidifying a casting product from an initial solidification portion toward a sprue portion under a high pressure of ² or more.